PASSWD(1)							  User utilities							 PASSWD(1)

NAME

       passwd - update a user's authentication tokens(s)

SYNOPSIS

       passwd [-k] [-l] [-u [-f]] [-d] [-n mindays] [-x maxdays] [-w warndays] [-i inactivedays] [-S] [username]

DESCRIPTION

       Passwd is used to update a user's authentication token(s).

       Passwd  is  configured to work through the Linux-PAM API.  Essentially, it initializes itself as a "passwd" service with Linux-PAM and uti-
       lizes configured password modules to authenticate and then update a user's password.

       A simple entry in the Linux-PAM configuration file for this service would be:

	#
	# passwd service entry that does strength checking of
	# a proposed password before updating it.
	#
	passwd password requisite 
		    /usr/lib/security/pam_cracklib.so retry=3
	passwd password required 
		    /usr/lib/security/pam_unix.so use_authtok
	#

       Note, other module-types are not required for this application to function correctly.

OPTIONS

       -k     The option, -k, is used to indicate that the update should only be for expired authentication tokens (passwords); the user wishes to
	      keep their non-expired tokens as before.

       -l     This  option  is	used  to  lock	the  specified account and it is available to root only. The locking is performed by rendering the
	      encrypted password into an invalid string (by prefixing the encrypted string with an !).

       --stdin
	      This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.

       -u     This is the reverse of the -l option - it will unlock the account password by removing the ! prefix. This  option  is  available	to
	      root  only.  By  default	passwd	will refuse to create a passwordless account (it will not unlock an account that has only "!" as a
	      password). The force option -f will override this protection.

       -d     This is a quick way to disable a password for an account. It will set the named account passwordless. Available to root only.

       -n     This will set the minimum password lifetime, in days, if the user's account supports password lifetimes.	Available to root only.

       -x     This will set the maximum password lifetime, in days, if the user's account supports password lifetimes.	Available to root only.

       -w     This will set the number of days in advance the user will begin receiving warnings that her password  will  expire,  if  the  user's
	      account supports password lifetimes.  Available to root only.

       -i     This  will set the number of days which will pass before an expired password for this account will be taken to mean that the account
	      is inactive and should be disabled, if the user's account supports password lifetimes.  Available to root only.

       -S     This will output a short information about the status of the password for a given account. Available to root user only.

Remember the following two principles
       Protect your password.
	      Don't write down your password - memorize it.  In particular, don't write it down and leave it anywhere, and don't place	it  in	an
	      unencrypted file!  Use unrelated passwords for systems controlled by different organizations.  Don't give or share your password, in
	      particular to someone claiming to be from computer support or a vendor.  Don't let anyone watch  you  enter  your  password.   Don't
	      enter your password to a computer you don't trust or if things Use the password for a limited time and change it periodically.

       Choose a hard-to-guess password.
	      passwd  will try to prevent you from choosing a really bad password, but it isn't foolproof; create your password wisely.  Don't use
	      something you'd find in a dictionary (in any language or jargon).  Don't use a name (including that of a spouse, parent, child, pet,
	      fantasy character, famous person, and location) or any variation of your personal or account name.  Don't use accessible information
	      about you (such as your phone number, license plate, or social security number) or your environment.  Don't use a birthday or a sim-
	      ple pattern (such as backwards, followed by a digit, or preceded by a digit. Instead, use a mixture of upper and lower case letters,
	      as well as digits or punctuation.  When choosing a new password, make sure it's unrelated to any previous password. Use  long  pass-
	      words  (say  8  characters  long).  You might use a word pair with punctuation inserted, a passphrase (an understandable sequence of
	      words), or the first letter of each word in a passphrase.

       These principles are partially enforced by the system, but only partly so.  Vigilence on your part will make the system much more secure.

EXIT CODE

       On successful completion of its task, passwd will complete with exit code 0.  An exit code of  1  indicates  an	error  occurred.   Textual
       errors are written to the standard error stream.

CONFORMING TO

       Linux-PAM (Pluggable Authentication modules for Linux).
       Note,  if  your	distribution of Linux-PAM conforms to the Linux Filesystem Standard, you may find the modules in /lib/security/ instead of
       /usr/lib/security/, as indicated in the example.

FILES

       /etc/pam.d/passwd - the Linux-PAM configuration file

BUGS

       None known.

SEE ALSO

       pam(8), and pam_chauthok(2).

       For more complete information on how to configure this application with Linux-PAM, see the Linux-PAM System Administrators' Guide at
       <http://parc.power.net/morgan/Linux-PAM/index.html>

AUTHOR

       Cristian Gafton <gafton@redhat.com>

Red Hat Linux							    Jan 03 1998 							 PASSWD(1)